Lubricants of organopolysiloxanes



United States Patent 3,122,507 LUBRICANTS 6F GRGANGPOLYEGXANES Walter Simmler, Cologne Mulheim, Germany, assignor to Farbenfabriken Bayer Aktiengeselischaft, Leverknsen, Germany, a corporation of Germany No Drawing. Filed Mar. 29, 1960, Ser. No. 18,245

Claims priority, application Germany Apr. 3, 1959 1 Claim. (Cl. 2524.6)

The present invention relates to a mixture of organopolysiloxanes which yields an excellent lubricant in an economically advantageous manner. Although organopolysiloxanes possess properties required for a lubricant, i.e. great stability to heat and cold in addition to a low dependence of their viscosity upon temperatures, they do not, however, ensure the stability of the lubricant film of good, purely organic oils under a high bearing pressure when halogen-free, hydrocarbon-substituted polysiloxanes are concerned.

It is also known that organopolysiloxanes carrying halogenated aryl radicals as a part of their hydrocarbon substituents have a substantially better lubricating power; with an increased proportion of these radicals, the Viscosity of the siloxane oils ultimately exceeds the permissible range for their application.

It is further known that a special kind of halogenated organosiloxane with an eminently high lubricating power may be obtained by a simple addition reaction of vinyl silane derivatives with hexa-halo-cyclopentadienes. In this reaction the vinyl radical is transformed by the addition of hexachloro-cyclopentadiene, for example, into the hexachloro-dicycloheptenyl radical of the formula LiJCl C Cl C Cl-C Clz-C Cl and units of the formula R' S1O wherein R and R denote hydrocarbon radicals, x denotes a. number between 0 and 2 and y a number between 1 and 3. By copolymerisation of siloxane units of the above two formulae in a suitable proportion it was to be expected to be able to produce polysiloxanes having a useful viscosity for each and every purpose; if, however, the viscosity lies within the technically important range between 10 and 300 centistokes, the siloxane chains contain only a small proportion of chloro-heptenylsiloxane units, and the lubricating power of such an oil, measured at the permissible pressure load, shows only a slight increase when compared with analogous polysiloxanes which do not contain a chloroheptenyl substituent.

The invention is based on the discovery that mixtures of smaller quantities of siloxanes which contain, among their radicals bound to silicon, a comparatively high proportion of chloroheptenyl, and larger quantities of specified chlorine-free, phenyland methyl-substituted polysiloxanes, surprisingly have properties which, in each case differ decisively from an essentially homogeneous oil of a siloxane copolymer of the same average composition as that of said mixtures. A lubricant according to the invention is a mixture of heptamethyl-(hexachlorodicycloheptenyl)-trisiloxane of the formula and five to twenty times its amount by weight of a liquid phenyl methyl polysiloxane consisting of chains endstopped by trimethyl siloxane units of siloxane units corresponding to one of the two formulae CsHa SiO

(LSKCHs) 3 and R -s ioi wherein each R of the second formula denotes methyl or phenyl with the proviso that within each of the siloxane chains the numerical proportion of the phenyl radicals to the methyl radicals is more than 1:5, preferably about 1:1 to 1:2.

The stability of the lubricant film of the mixtures according to the invention is nearly of the same magnitude as that of the first-named mixture component used alone, and greater than that of the known copolymers of the same average composition as the combination obtained according to the invention by mere mixing. Thus, with the latter only the problem is solved of producing a lubricating oil which meets all three essential requirements, at the same time, i.e. first the oil is only slightly dependent on the temperature in its fluid state, which is a general characteristic of all organopolysiloxanes, thus differing from purely organic oils, secondly it shows the stability of the lubricating film that is surprisingly high for organosiloxanes which, as is known, the hexachloro-dicycloheptenylsilyl group is capable of bringing about so that its lubricating power attains that of mineral oil products, and third that the viscosity may be adjusted to the conditions required for each and exery purpose within a Wide range, and all this in a simple and an economically advantageous manner.

The following examples are given for the purpose of illustrating the invention.

Examples Mixtures of 10 parts by weight of heptamethyl- (hexachloro-dicycloheptenyl)-trisiloxane of the structure defined above and parts by weight of a linear phenylmethyl polysiloxane whose individual chain members consist in each case of the siloxane units indicated below and whose chains are end-stopped by trimethyl siloxane units, are tested in the well-known Almen-Wieland machine as to the load of the lubricating film, resulting in the maximum loads given below, involving corrosion of the elements of the test bearing; the viscosity values given are measured at 20 C.

Si O

(C H3) 3SiO The above mixture component alone has a viscosity of 10 centistokes and a maximum load of kg; the mixture has a viscosity of 13 centistokes and a maximum load of 1300 kg.

a (2) (C H SiO and (CH SiO in a ratio of 1:1

( 3) (C H SiO and (CH SiO in a ratio of 121.5

The maximum load of the mixture is 1000 kg, the other values are approximately the same as those given under (2).

The aforesaid chloroheptenyl component alone has a viscosity of 100 centistokes and a maximum load of 1000 kg. in the Almen-Wieland machine. This good lubricating power which is known as such is lost to a large extent by a mixed condensation of said ch1oroheptenyl-siloxane units with other bifunctional organosiloxane units in order to adjust the viscosity of the oil to any desired purpose. It was not to be expected that instead of a mixed condensation only a simple mixing would lead to the desired result, that only a phenylmethyl polysiloxane of a very limited class was to be suitable as a second mixing component for this purpose, and that by this admixture of a component low load-bearing itself, in a fiveto twenty-fold amount no perceptible loss in lubricating power would take place, a result which may be explained by the assumption that the active component of the mixtures according to the invention is adsorbed at the phase limit of the siloxane oil to the metal of the bearings.

For reason of comparison a series of siloxane oils of a composition other than that according to the invention were tested, with the result that the load limits were less than half of the figures indicated above. In each individual case the following was found:

(4) A mixture similar to those mixtures according to the invention indicated above under (2) and (3) and difiering from these two essentially only in that the ratio of the diphenyl-siloxane units to the dimethyl-siloxane units was 1:5, resulted in a maximum load of 350 kg.

(5) Another similar mixture of a centistokeviscosity containing a thinly liquid phenylmethyl polysiloxane component, in a diphenylsiloxane-to-dimethyl siloxane ratio of 1:3, permitted only a 250 kg. load.

(6) Similar mixtures with phenyl-free dimethyl siloxane oils of a viscosity of 10 and 300 centistokes resulted in a maximum load of 150 and 250 kg. respectively.

(7) A copolymer prepared in known manner by hydrolysis of a mixture of trimethyl-chlorosilane, dimethyl-dichlorosilane, diphenyl-dichlorosilane and methyl-(hexachloro-dicycloheptenyl)-dichlorosilane, the ratio of the different substituents of silane being approximately the same as that of the above mixture according to the invention indicated under (2), and also having a viscosity of 300 centistokes, resulted in a maximum load of 400 kg.

A (8) A polysiloxane having on the whole a similar composition and a viscosity of 300 centistokes was pre-.

pared in known manner by hydrolysis of a mixture of trimethyl-chlorosilane, dimethyl-dichlorosilane, diphenyldichlorosilane and vinylmethyl-dichlorosilane, and subsequent chemical addition of hexachloro-cyclopentadiene. The maximum load was 25 0 kg.

(9) With a phenylmethyl polysiloxane as indicated above under (2) there is admixed instead of heptamethyl- (hexachloro-dicycloheptenyl)-trisiloxane, 10 percent by weight of a trisiloxane diol of the formula C 01 C C1 3O1C 012-0 01 OSi (CH3) 3 311 OHSi -CH3 OSi (CF93 and 95-80 percent by weight of a liquid phenyl methylpolysiloxane consisting of chains, end-stopped by trimethylsiloxane units, of siloxane units which are selected from the group consisting of the units C5115 S'iO- )Si(OHs)s and wherein each R of the second unit is selected from the group consisting of methyl and phenyl with the proviso that within the sum of the said second units of each siloxane chain the ratio of the number of phenyl radicals to the number of methyl radicals is about 1:1 to 1:2.

References Cited in the file of this patent UNITED STATES PATENTS 2,491,843 Wilcock Dec. 20, 1949 2,67,089 Kleiman Dec. 14, 1954 FOREIGN PATENTS 539,624 Canada Apr. 16, 1957 776,706 Great Britain June 12, 1957 

